Endogenous bFGF Research Articles

Basic Fibroblast Growth Factor and Receptor Expression in Human Ovarian Cancer

Basic fibroblast growth factor (bFGF) and other members of the FGF family share several biological properties that have the potential to mediate neoplastic cell growth. To test the hypothesis that bFGF may play a role in human ovarian cancer cell growth, three ovarian cancer cell lines, A90, A121(P), and A121(A), were investigated for their ability to respond to bFGF as a mitogen, to express endogenous bFGF protein or message for FGF proteins, and to exhibit FGF receptor or its message. Addition of bFGF to cultures of all three cell lines maintained in chemically defined media resulted in a statistically significant increase in cell number. Cell extracts from A90, A121(P), and A121(A) contained an immunoreactive protein that comigrated with hr-bFGF by Western blot analysis. Several bands of higher molecular weight were also noted. Immunohistochemical staining for bFGF demonstrated a cytoplasmic distribution of bFGF in the three cell lines. Both high- and low-affinity binding sites for human recombinant bFGF (hr-bFGF) were expressed by all three lines. High-affinity sites varied from 2700 sites per cell (Kd = 29 pM) to 13,500 sites per cell (Kd = 71 pM). All three cell lines were screened for mRNA expression for seven FGF proteins and four FGF receptors. In all three lines, mRNA for FGF2 (bFGF) was detected by PCR analysis, and in two lines, mRNA for FGF1 (aFGF) and FGF5 were also found. The FGFRI receptor subtype (flg) was common to all of the cell lines. Finally, suramin inhibited proliferation of A90 and A121 (P and A) with IC50's of 60 and 210 μg/ml, respectively. This is consistent with the A90 cell line having higher levels of endogenous bFGF and flg and therefore being more responsive to suramin inhibition than the A121 cell line. The results indicate that these ovarian cancer cell lines can produce bFGF as well as other members of the FGF family of genes and have the ability to respond to bFGF.

Tumor cells secrete an angiogenic factor that stimulates basic fibroblast growth factor and urokinase expression in vascular endothelial cells.

Culture medium conditioned by human SK-Hep1 hepatoma cells or mouse S180 sarcoma cells rapidly up-regulates endothelial cell expression of basic fibroblast growth factor (bFGF) and induces formation of capillary-like structures by vascular endothelial cells grown on three-dimensional fibrin gels (in vitro angiogenesis). Incubation of endothelial cells with the tumor cell-conditioned media also results in increased expression of urokinase plasminogen activator (uPA), a key component of the proteolytic system required for cell invasion and capillary formation. Although the tumor cell-conditioned media contain no bFGF, addition of anti-recombinant bFGF IgG abolishes the up-regulation of uPA and blocks in vitro angiogenesis. This indicates that both the increase in uPA production and formation of capillary-like structures are mediated by endogenous bFGF expressed by the endothelial cells. Both the bFGF/uPA-inducing activity and the angiogenic activity of SK-Hep1 cell-conditioned medium copurify with a relatively acid-resistant peptide that has moderate affinity for heparin and M(r) < 18 kDa > 3.5 kDa. Known cytokines with similar biochemical features do not possess the same biological activity. These findings indicate that angiogenesis can be mediated by endothelial cell bFGF through an autocrine mechanism and that the bFGF-inducing peptide may represent a novel tumor-derived angiogenic factor that modulates in endothelial cells the concerted expression of cytokines and proteolytic enzymes required for capillary formation.

Correlation of transformation from epithelial to mesenchymal‐like morphology and endogenous bFGF levels in human nasopharyngeal carcinoma cells

CG-1 human nasopharyngeal carcinoma cells in monolayer culture formed both cohesive, epithelial-like colonies and scattered, fibroblastic-like colonies in mixed proportions. In the presence of exogenously added bFGF (4 ng/ml), about 85% of the colonies formed were fibroblastic-like. CG-1 cells were capable of synthesizing and releasing bFGF, and, when compared by the immunological method, cells in fibroblastic-lke colonies were found to contain higher levels of endogenous bFGF than cells in the epithelial-like colonies. Furthermore, cells in the peripheral region of the epithelial-like colonies, which were fibroblastic-like in morphology, also appeared to contain higher levels of endogenous bFGF. In addition, in the presence of suramin, neutralizing antibody to bFGF, or neutralizing antibodies to bFGF and EGF, the number of cohesive colonies formed was greatly increased. Moreover, addition of the 2 M NaCl-eluted heparin-Sepharose fraction of the CG-1 cell-coditioned medium promoted the formation of dispersed colony in a dose-dependent manner. The results suggest that bFGF can regulate CG-1 cell phenotype in an autocrine manner.

Stimulation of fracture repair by recombinant human basic fibroblast growth factor in normal and streptozotocin-diabetic rats.

The effect of local application of recombinant human basic fibroblast growth factor (rhbFGF) on fracture repair was examined using normal rats and streptozotocin-diabetic rats with impaired repairing ability. Immediately after fracturing the fibula, rhbFGF was applied by a single injection to the fracture site. Application of rhbFGF increased the volume and mineral content of callus in a dose-dependent manner in both normal and diabetic rats, and callus formation of diabetic rats was stimulated to levels similar to those in nontreated normal rats. The marked effect of rhbFGF on fracture repair was associated with an improvement in the mechanical properties of the healing fibula in both normal and diabetic rats. Immunohistochemical staining showed that endogenous bFGF was widely distributed in normal rats 1 and 3 weeks after fracture, especially in the soft callus and periosteum, whereas much less bFGF was detected in diabetic rats. Insulin treatment of diabetic rats restored the immunostaining for bFGF. These results demonstrate that bFGF is expressed during the early stage of fracture repair, and that the impaired fracture-repairing ability in diabetic rats is associated with reduced expression of bFGF at the fracture site. A single application of bFGF immediately after fracture not only facilitates the repair process in normal rats, but also recovers the impaired repairing ability in diabetic rats. These results suggest that local application of bFGF may facilitate bone union in patients with impaired as well as normal repairing ability.

Basic fibroblast growth factor decreases elastin production by neonatal rat lung fibroblasts.

During pulmonary development, there is a burst in elastin synthesis by interstitial fibroblasts coincident with the period of alveolar septal elongation. Little is known about the regulation of elastin synthesis by these cells, although several endocrine and paracrine factors influence lung fibroblast elastin production. Because alveolar septal elongation is accompanied by a decrease in capillary endothelial cell mitosis, we have hypothesized that a reduction in basic fibroblast growth factor (bFGF), an endothelial cell mitogen, may occur concomitantly with an increase in elastin synthesis. This temporal relationship suggests that bFGF may influence elastin production by interstitial fibroblasts. Therefore, we have examined the effects of bFGF on elastin production by postconfluent, serum-free cultures of lipid interstitial fibroblasts (LF). Elastin production was quantitated by analyzing the incorporation of 3H-valine into the soluble elastin precursor tropoelastin (TE). Exogenous bFGF decreased the quantity of newly synthesized TE in the culture media and cell layers of LF. The level of newly synthesized TE in the media was decreased to 36% and 48% of the unexposed control when LF were exposed for 48 h to 10 or 75 ng/ml bFGF, respectively. Northern analysis demonstrated that the decrease in TE was accompanied by a similar decrease in elastin mRNA. Transient transfection experiments using an elastin promoter/CAT gene construct demonstrated that bFGF exposure decreased elastin promoter activity. These results suggest that bFGF decreases elastin transcription. Exposure to an anti-bFGF antibody neutralized endogenous bFGF and increased soluble elastin production by LF. Our studies indicate that exogenous and endogenous bFGF can suppress elastin production by LF. A similar effect may occur in the intact lung during development or chronic inflammation.

The development and enhancement of the collateral circulation in an animal model of lower limb ischaemia.

In an animal model of hind limb ischemia we documented the levels of endogenous basic fibroblast growth factor (bFGF) in control and ischaemic hind limbs, and evaluated the response to the administration of exogenous recombinant bFGF and heparin. Variations in this model were tested for their ability to alter the development of the collateral circulation. Recovery after acute arterial occlusion was significantly delayed by immediate bilateral mirror-image arterial ligations, when compared with either unilateral arterial ligation or delayed contralateral ligations performed after 2 months. If the major veins were also occluded all limbs developed gangrene, tissue loss and a marked delay in the recovery of blood flow, while none of the animals with unilateral arterial ligations developed gangrene. This indicates that the recovery in blood flow during the acute phase in this model is dependent on collateral vessels from the contralateral iliac artery and that major venous occlusion impedes the development of collateral vessels. Lumbar sympathectomy did not alter the recovery of blood flow after arterial occlusion, suggesting that collateral blood flow is not significantly influenced by autonomic neural supply. Following arterial occlusion there was a ten-fold increase in the levels of endogenous bFGF in all ischaemic muscle groups. Intramuscular implantation of bFGF in heparin-sepharose pellets at the time of arterial ligation markedly enhanced the blood flow for 3 weeks compared with untreated ischaemic limbs. A further increment in blood flow occurred if an additional dose of bFGF was administered 4 weeks after ligation.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of chondrogenesis: requirement for synergistic interaction of basic fibroblast growth factor and transforming growth factor-beta.

Interactions between the epithelial anlage of the developing mouse inner ear and its associated periotic mesenchyme control the differentiation of the cartilaginous otic capsule. Transforming growth factor-beta 1 (TGF-beta 1) is a naturally occurring signal peptide that is present in these tissues at times of active differentiation and morphogenesis. Previous studies have shown that TGF-beta 1 alone is not a sufficient stimulus to initiate chondrogenesis in cultured periotic mesenchyme. In this study, we provide evidence that basic fibroblast growth factor (bFGF) can elicit a specific but limited chondrogenic response in cultured periotic mesenchymal cells. We also demonstrate that simultaneous addition of bFGF and TGF-beta 1 to cultured periotic mesenchyme results in a full chondrogenic response comparable to that which occurs when periotic mesenchyme is grown in the presence of its natural inductor tissue (i.e. otic epithelium). Utilizing antibodies directed against bFGF, we show localization of endogenous bFGF in the otic epithelium in vivo and in mixed epithelial-mesenchymal cultures. Additionally, we demonstrate the presence of FGF-like activity in medium conditioned by otic epithelium. Blocking of epithelial elicited chondrogenesis by a combination of both alpha bFGF and alpha TGF-beta 1 antibodies provides further evidence of the necessity for these growth factors in the chondrogenic differentiation of periotic mesenchyme in vitro. Our results suggest a role for both bFGF and TGF-beta 1 in the regulation of chondrogenesis during otic capsule formation in situ.

Stimulation by zinc of cultured vascular endothelial cell proliferation: Possible involvement of endogenous basic fibroblast growth factor

Vascular endothelial cells from bovine aorta were cultured with zinc sulfate (20 μM or less) for 24 h and labeled with [ 3H]thymidine or [ 14C]leucine during the last 3 h of the culture. It was found that the cell number was significantly increased by zinc alone; the incorporation of both [ 3H]thymidine and [ 14C]leucine was also stimulated by the metal. The stimulation by zinc occurred in the presence or absence of exogenous basic fibroblast growth factor (bFGF). However, other heavy metals including copper, manganese and nickel did not exhibit such a stimulatory effect, suggesting that zinc plays a particular role in endothelial cell proliferation. Stimulation of the [ 3H]thymidine incorporation by zinc disappeared in the presence of either cycloheximide or anti-bFGF IgG; in addition, a lipoxygenase inhibitor nordihydroguaiaretic acid diminished the zinc stimulation but a cyclooxygenase inhibitor indomethacin did not exhibit such an inhibitory effect. These results indicated that zinc stimulated the proliferation of endothelial cells through the lipoxygenase pathway which mediates the stimulation by endogenous bFGF. In other words, the metal may amplify the endogenous bFGF-dependent proliferation of the cells.

Basic fibroblast growth factor experimentally induced choroidal angiogenesis in the minipig.

Basic fibroblast growth factor (bFGF), a soluble mitogen, has been isolated and purified from various organs, including the retina. In vivo angiogenic activity of bFGF has been demonstrated with several assays. An experimental model of choroidal neovascularization was developed in the mini pig by perfusion of recombinant human bFGF through an osmotic minipump. Endogenous bFGF and bFGF receptors were localized in the normal pig retina by immunohistochemistry and autoradiography after binding. The perfusion of exogenous bFGF induced well-organized new vessels along the last 3 mm of the catheter in the suprachoroidal space. This neovascularization did not penetrate the normal Bruch's membrane. Vascular cells (identified by von Willebrand factor antibody staining) increased in number and in surface from the proximal part to the end of the intraocular catheter in all bFGF perfused eyes. In eyes perfused with phosphate buffered saline (controls), but not in the bFGF perfused eyes, an inflammatory response occurred (identified by a macrophage specific antibody). These results demonstrate that choroidal angiogenesis can be achieved without an inflammatory response by perfusing an excess of bFGF in the suprachoroidal space.

Heparin stimulates the proliferation of bovine aortic endothelial cells probably through activation of endogenous basic fibroblast growth factor

We investigated the effect of heparin on the proliferation of cultured bovine aortic endothelial (BAE) cells. Heparin increased DNA synthesis in BAE cells in a concentration-dependent manner. The DNA synthesis increased by 2 to 2.5-fold with 1 mg/ml of heparin after 48 h incubation without serum and exogenous fibroblast (heparin-binding) growth factors. The stimulating effect of heparin decreased with the diminishing number of monosaccharide units which constitute heparin. By the addition of a neutralizing antibody to basic fibroblast growth factor (bFGF), the stimulating effect of heparin decreased, whereas an antibody to acidic fibroblast growth factor (aFGF) had no effect. The culture medium conditioned by heparin-treated BAE cells stimulated DNA synthesis in Balb/3T3 fibroblasts that proliferate in response to bFGF. The mitogenic activity of the conditioned medium was supressed by the antibody to bFGF. However, heparin did not increase bFGF mRNA level in BAE cells. These results suggest that heparin stimulates the proliferation of BAE cells by the activation of endogenous bFGF, but not by the induction of its synthesis.

Upregulation of urokinase receptor expression on migrating endothelial cells

One of the phenotypic hallmarks of migrating endothelial cells, both in vivo and in vitro, is expression of the urokinase-type plasminogen activator (u-PA), a key mediator of extracellular proteolysis. In the study reported here, we have used an in vitro model of endothelial cell migration to explore the mechanism of this phenomenon. We have found that wounding of an endothelial cell monolayer triggers a marked, rapid and sustained increase in expression of a specific high-affinity receptor for u-PA (u-PAr) on the surface of migrating cells. Migrating cells displayed an increase in the levels of u-PA and u-PAr mRNAs, and this increase was mediated by endogenous basic fibroblast growth factor (bFGF). We also show that the increase in u-PA activity on migrating cells can be accounted for by an increase in receptor-bound u-PA, and that the increase in activity is also dependent on endogenous bFGF. These results demonstrate that the expression of plasmin-mediated proteolytic activity by migrating endothelial cells is a consequence of increased production of both u-PA and its receptor, and that this in turn is mediated by endogenous bFGF. This suggests that u-PA, produced at increased levels by migrating cells, binds to u-PAr whose expression is upregulated on the same cells. These observations are in accord with the postulated role of u-PAr in mediating efficient and spatially restricted extracellular proteolysis, particularly in the context of cell migration.

Thromboxane A2 stimulates vascular smooth muscle hypertrophy by up-regulating the synthesis and release of endogenous basic fibroblast growth factor

We have shown previously that thromboxane A2 stimulates hypertrophy of cultured rat aortic smooth muscle cells defined as protooncogene expression and protein synthesis without DNA synthesis or cellular proliferation (Dorn, G.W., II, Becker, M.W., Davis, M.G. (1992) J. Biol. Chem. 267, 24897-24905). Since endogenous growth modulators could possibly regulate vascular smooth muscle growth to this vasoconstrictor, we tested the hypothesis that thromboxane-stimulated vascular smooth muscle hypertrophy was due to increased expression of endogenously produced basic fibroblast growth factor (bFGF). The thromboxane mimetic (15S)-hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5Z,13E-dienoic acid (U46619) (1 microM) increased cultured rat aorta derived smooth muscle cell immunoreactive bFGF content by 331 +/- 40% over untreated controls after 24 h. Co-incubation of vascular smooth muscle cells with a specific antisense oligodeoxynucleotide (AS) against codon 60 of bFGF coding sequence reduced thromboxane-stimulated bFGF expression by 72 +/- 5% and prevented thromboxane-stimulated hypertrophy (nonsense oligonucleotide had no effects). Addition of exogenous bFGF (20 ng/ml) restored growth to AS-treated/thromboxane-stimulated vascular smooth muscle cells. Furthermore, addition to the culture medium of neutralizing antibody against bFGF inhibited U46619-stimulated vascular smooth muscle hypertrophy by 69 +/- 17%, whereas nonimmune IgG had no effect. Since protein tyrosine phosphorylation is a cell signal associated with growth, thromboxane-stimulated tyrosine phosphorylation was also examined. Exposure to 1 microM U46619 for 10 min increased vascular smooth muscle immunoreactive phosphotyrosine content of 130-144-, 86-, 80-, 75-, and 58-kDa proteins. The tyrosine kinase inhibitor herbimycin A (5 microM) prevented thromboxane-stimulated tyrosine phosphorylation, but not thromboxane-stimulated hypertrophy, suggesting that tyrosine phosphorylation was not required for thromboxane-stimulated vascular smooth muscle growth. These results indicate that increased expression and release of endogenous bFGF, but not direct tyrosine phosphorylation, mediates the hypertrophic vascular smooth muscle response to thromboxane.

Carboxyl-terminal heparin-binding fragments of platelet factor 4 retain the blocking effect on the receptor binding of basic fibroblast growth factor.

Platelet factor 4 (PF‐4) blocks the binding of basic fibroblast growth factor (bFGF) to its receptor. In the present study, we constructed carboxyl‐terminal fragments, which represent the heparin‐binding region of the PF‐4 molecule, and examined whether these synthetic peptides retain the blocking effects on the receptor binding of bFGF. Synthetic peptides inhibited the receptor binding of bFGF. Furthermore, they inhibited the migration and tube formation of bovine capillary endothelial cells in culture (these phenomena are dependent on endogenous bFGF).

Restitution of frog gastric mucosa in vitro: Effect of basic fibroblast growth factor

Background: Rapid re-epithelialization after superficial gastric mucosal injury is caused by migration of persisting viable epithelial cells. Basic fibroblast growth factor (bFGF) has been reported to enhance the healing of experimental duodenal ulcer, but its mode of action is unclear. The present experiments examine whether an effect of bFGF on restitution might contribute to such healing. Methods: Paired halves of bullfrog fundic gastric mucosa in Ussing chambers were injured by luminal exposure to 1 mol/L NaCl for 10 minutes. Results: Luminal protamine or suramin, both known to interfere with endogenous bFGF, significantly inhibited electrophysiological recovery at neutral luminal pH (pHL). Luminal sucrose octasulfate, which prevents acid degradation of bFGF, and an exogenous, acid-resistant form of bFGF allowed electrophysiological recovery at a pHL of 3.0 that completely prevented restitution in control tissues. Electrophysiological recovery correlated well with morphological restitution. The presence of endogenous bFGF in normal and restituting bullfrog mucosa was confirmed by positive staining with a monoclonal antibody. Conclusions: It is concluded that rapid epithelial repair after surface injury is at least in part mediated by bFGF.

Wachstumsfaktor-induzierte Stimulation der Proteoglykansynthese in Kornea-Endothelzellen

Cultured bovine corneal endothelial cells (CEC) synthesize heparan sulfate and dermatan sulfate containing proteoglycans and distribute them between different compartments. [35S]sulfate labelled proteoglycans are found associated with the cell layer, secreted into the culture medium and deposited into the underlaying extracellular matrix. In the presence of basic fibroblast growth factor (bFGF)-a strong mitogen for CEC-subconfluent cells incorporate [35S]sulfate into the sulfated proteoglycans at a rate three times higher as compared with the proteoglycans of CEC in the absence of bFGF. The enhanced proteoglycan synthesis is accompanied with a shift in the proteoglycan distribution pattern. While in control cells the cell-associated heparan sulfate accounts for about 30% of the total glycosaminoglycans under the influence of bFGF the HS percentage increases to approximately 60%. CEC synthesize and deposit endogenous bFGF into the extracellular matrix. Heparitinase treatment of the extracellular matrix releases bFGF activity which is able to stimulate the 35S incorporation into proteoglycans in a comparable manner as exogenous bFGF but does not influence the proteoglycan distribution pattern. Pretreatment of the matrix-bound bFGF activity with polyclonal antibodies against bFGF abolishes its stimulating activity.

Light- and electron-microscopic localization of basic fibroblast growth factor in adult rat retina.

An antiserum against basic fibroblast growth factor (bFGF) was characterized by immunoblot and used to localize bFGF-immunoreactivity in the adult rat retina. Crude homogenate of the retina, when examined with immunoblotting, exhibited a main band with the same molecular weight (18kDa) as bFGF. Light microscopic immunohistochemistry demonstrated intense bFGF staining in the photoreceptor outer segments and the outer plexiform layer, and weak immunostaining in some cells of the outer nuclear layer, inner nuclear layer and ganglion cell layer. The most intense bFGF-immunoreactivity was noted in glial (Müller) cells with vertically oriented thin processes. There were also immunoreactive pigment epithelial cells and mesenchymal cells in the choroid. Under electron microscopy, the outer plexiform layer was found to contain immunoreactive products exclusively in the axon terminals of photoreceptor cells which formed synapses with bipolar cell processes. The more widespread and uneven localization of bFGF-immunoreactivity in the mature rat retina than previously demonstrated suggests that endogenous bFGF is involved in complex physiological events other than retinal regeneration and histogenesis.

Upregulation of fibroblast growth factor-receptor messenger RNA expression in rat brain following transient forebrain ischemia

Recently, we demonstrated that transient forebrain ischemia in rats leads to an early and strong induction of basic fibroblast growth factor (bFGF) synthesis in astrocytes in the injured brain regions. In this study, in order to clarify the targets of such raised endogenous bFGF levels, the messenger RNA (mRNA) expression of its receptors (flg and bek) in the hippocampus following transient forebrain ischemia induced by four-vessel occlusion for 20 min was investigated using an in situ hybridization technique. Transient forebrain ischemia induced an increase in the number of flg mRNA-positive cells from an early stage (24 h after ischemia) in the hippocampal CA1 subfield where delayed neuronal death occurred later (48-72 h after ischemia). This increase became more marked with the progression of neuronal death and was still evident in the same area 30 days later. The time course of the appearance and distribution pattern of flg mRNA-positive cells in the CA1 subfield were quite similar to those of bFGF mRNA-positive cells. On the other hand, in situ hybridization for bek mRNA showed only slight and transient (observed 72 h and 5 days after ischemia) increases in the number of mRNA-positive cells in the CA1 subfield following ischemia. The use of in situ hybridization and glial fibrillary acidic protein immunohistochemistry in combination demonstrated that the cells in the CA1 subfield that exhibited ischemia-induced flg or bek mRNA expression were astrocytes. These data indicate that transient forebrain ischemia induces upregulation of fibroblast growth factor-receptor expression, accompanied by increased bFGF expression in astrocytes, and suggest that the increased astrocytic bFGF levels in injured brain regions act on the astrocytes via autocrine systems and are involved in the development and maintenance of astrocytosis.

Inhibition of smooth muscle cell proliferation in injured rat arteries. Interaction of heparin with basic fibroblast growth factor.

Heparin inhibits smooth muscle cell (SMC) proliferation after arterial injury by mechanisms that have yet to be defined. Since the initiation of SMC proliferation is mediated by basic fibroblast growth factor (bFGF), we have investigated the possibility that heparin inhibits SMC proliferation by displacing bFGF from the arterial wall. Using a rat carotid artery model of balloon catheter injury, we demonstrate that a bolus injection of heparin depletes the arterial wall of both systemically administered bFGF and of endogenous bFGF. Heparin, however, does not reduce the bFGF content of unmanipulated arteries. Further, a single injection of heparin given at the time of balloon injury reduces SMC proliferation by 55% but has no effect when given 6 h after injury. SMC proliferation induced in a denuded artery by injection of bFGF is inhibited almost completely by a bolus injection of heparin; however, pretreatment with a bolus of heparin does not prevent SMC from responding to a subsequent bolus of bFGF. These experiments suggest that heparin can inhibit SMC proliferation in part by removal of released bFGF from sites of injury.

Basic fibroblast growth factor increases junctional communication and connexin 43 expression in microvascular endothelial cells.

We have analyzed the effect of basic fibroblast growth factor (bFGF) on junctional communication (coupling) and connexin 43 (Cx43) expression in bovine microvascular endothelial (BME) cells. In control confluent cultures, the incidence of coupling, as assessed by the intercellular transfer of microinjected Lucifer Yellow, was limited to 13% of injected cells, and decreased to 0% with time in culture. After exposure to bFGF (3ng/ml), the incidence of coupling was increased in a time-dependent manner, reaching a maximum of 38% of microinjected cells after 10-12 hours. The extent of coupling, as assessed by scrape loading, was maximally increased 2.1-fold 8-9 hours after addition of bFGF. bFGF also induced a 2-fold increase in Cx43 as assessed by Western blotting, and increased Cx43 immunolabelling at contacting interfaces of adjacent BME cells. Cx43 mRNA was likewise increased after exposure to bFGF in a time- and dose-dependent manner, with a maximal 6-7-fold increase after a 4 hour exposure to 3-10ng/ml. Finally, the increase in coupling and Cx43 mRNA expression observed after mechanically wounding a confluent monolayer of BME cells was markedly reduced by antibodies to bFGF, which have previously been shown to inhibit migration. Taken together, these results indicate that exogenous and endogenous bFGF increase intercellular communication and Cx43 expression in microvascular endothelial cells. We propose that the bFGF-mediated increase in coupling is necessary for the coordination of endothelial cells during angiogenesis and other vessel wall functions.

Phosphorothioate antisense oligonucleotides against basic fibroblast growth factor inhibit anchorage-dependent and anchorage-independent growth of a malignant glioblastoma cell line.

Basic fibroblast growth factor (bFGF) is a broad spectrum mitogen for many cells of neuroectodermal origin, including glial cells. The human malignant glioblastoma cell line U87-MG expresses high steady state levels of the bFGF mRNA and contains abundant stores of biologically active bFGF protein. In the present study we have examined the contribution of endogenous bFGF to the autocrine growth of these cells. Using reverse transcription-polymerase chain reaction, U87-MG cells were shown to express the mRNAs for both bFGF and the bFGF receptor, confirming the existence of the basic requirements for an autocrine loop. Addition of 5 microM bFGF-specific antisense oligonucleotide to U87-MG cultures significantly inhibited the growth rate of these cells within 48 h and blocked proliferation beyond 2 days. The corresponding bFGF-specific sense oligonucleotide did not significantly inhibit cell proliferation over the course of these experiments. Similarly, antisense oligonucleotides significantly inhibited colony formation in soft agar, while the sense sequence was without effect. Western blotting with antihuman bFGF revealed that U87-MG cells synthesize three isoforms of bFGF, approximately 18, 23, and 25 kilodaltons (kDa) in size. The 23- and 25-kDa isoforms together comprise approximately 80% of the total cellular stores of bFGF. Antisense treatment for 4 days reduced the abundance of the 23- and 25-kDa isoforms by 64-74%, but had little effect on the 18-kDa isoform. The inhibitory effect of the antisense oligonucleotides on anchorage-dependent proliferation was reversed by the addition of recombinant 18-kDa human bFGF.(ABSTRACT TRUNCATED AT 250 WORDS)